1. Field of the Invention
This invention relates to an improvement in processes for the production of acid chlorides and more particularly to a process for recovering acid chlorides from mixtures containing the same.
2. Description of the Prior Art
The acid chlorides with which this invention is primarily concerned are known intermediates in the production of antimicrobial compounds such as 3-methyl-7-aminodecephalosporanic acid derivatives, see U.S. Pat. No. 3,129,224. The entire disclosure of this patent is incorporated herein by reference.
Generally, an acid is reacted with a chlorinating agent to produce a reaction mixture containing the desired acid chloride. This reaction mixture is then purified by distillation either continuously or batchwise, preferably under vacuum at a low temperature to prevent degradation.
During the above-described chlorination and distillation processes, by-products, polymers and degradation products are produced which cause a decrease in yield of the desired acid chloride. In particular, the acid chlorides are sensitive to temperature and tend to degrade and/or polymerize when subjected to excessive temperatures for long periods of time such as those encountered in distillation. The resultant degradation products can foul heat transfer surfaces. In order to overcome this problem, it has been proposed to recover the acid chlorides from the reaction mixture by the use of wiped and thin film evaporators; however, these evaporation devices are expensive to use and operate, and fouling of the equipment and residue removal can be a problem.
It is an object of this invention to provide an improved method for recovering acid chlorides from mixtures containing the same.
It is another object of this invention to recover acid chlorides from reaction mixtures at increased yields.